Wool combing is an important step in the manufacture of worsted yarns. The wool, after carding or "preparing", is passed through a combing machine which continues the process, combing out short fibers and aligning the long fibers accurately alongside each other. The combed wool coming out of this process in the form of an untwisted strand called `top`, is then drawn out into roving and spun by twisting it into a yarn. The long fibers, lying parallel to one another in the combed roving, are able to cling tightly together on twisting to form a fine strong worsted yarn. During the process of combing, a certain proportion of fibers is broken and removed in this process as noil.
The most commonly used combing machine is the French (or Continental) machine which is typically used for combing of "thin" fibers (e.g. cross-breds) with a length of 90 mm to 250 mm. Whatever type of combing machine is used, a "comb" which will generally comprise a plurality of pins, tines or the like) is drawn relatively through the previously carded wool sliver. During this combing process, the long wool fibres in the sliver are arranged in generally parallel formation, and unwanted material is removed from the sliver. This unwanted material includes short fibres, the so-called "noil", which need to be eliminated because it is the longer fibres which contribute to the strength of the yarn. However, the mechanical action of the comb in passing through the wool will cause some fibre breakage and formation of additional noil.
It has previously been proposed to heat the pins of a Noble (or English) comb with view to improving combing performance, see for example Brearley, A., "Worsted", Sir Isaac Pitman & Sons Ltd., 1964 which discloses at page 45 the provision of a steam-chest beneath the large circle to provide heat for softening the oil on the fibres and facilitating the drawing of the fibres through the pins.
The fact that a slightly lower percentage of noil is obtained by heating the pins of the Noble Comb, has been confirmed by Townend, et al, see "The scientist looks at the Wool Industry-Combing"--Wool Sci. Rev., 3, No. 11 (1953).
A study on the effect of heating the top comb in rectillinear combing has been reported by Godawa and Turple (see Sawtrl Bulletin, September 1974, Vol. 8, pages 48-55) who conclude that percentage noil decreased slightly as the temperature of the top comb was increased from room temperature to 60.degree. C., with apparently no further reduction when the top comb was heated above 60.degree. C.